Bottom Line:
Further, nicotinic suppression of NF-κB-induced transcriptional activity in NK cells is dependent on nAChR β2.This nAChR subtype also plays a large role in the NK cell-mediated control of melanoma lung metastasis, in a murine lung metastasis model exposed to nicotine.Our findings suggest nAChR β2 as a prominent pathway for nicotine induced impairment of NK cell functions which contributes to the occurrence of smoking-related pathologies.

ABSTRACTCigarette smoke exposure markedly compromises the ability of the immune system to protect against invading pathogens and tumorigenesis. Nicotine is a psychoactive component of tobacco products that acts as does the natural neurotransmitter, acetylcholine, on nicotinic receptors (nAChRs). Here we demonstrate that natural killer (NK) cells strongly express nAChR β2. Nicotine exposure impairs the ability of NK cells to kill target cells and release cytokines, a process that is largely abrogated by nAChR β2 deficiency. Further, nicotinic suppression of NF-κB-induced transcriptional activity in NK cells is dependent on nAChR β2. This nAChR subtype also plays a large role in the NK cell-mediated control of melanoma lung metastasis, in a murine lung metastasis model exposed to nicotine. Our findings suggest nAChR β2 as a prominent pathway for nicotine induced impairment of NK cell functions which contributes to the occurrence of smoking-related pathologies.

pone-0057495-g004: Nicotine inhibits NF-κB activation in NK cells through nAChR β2.NK cells were sorted from splenocyte single cell suspensions of RAG2−/− and RAG2−/−β2−/− mice. NF-κB and IKKα mRNA of sorted NK cells in β2+/+ or β2−/− mice received nicotine (Nic) was measured by qRT-PCR. The data of one experiment out of two performed is shown, n = 3–4 mice/group. P values, Student’s t-test, *p<0.05.

Mentions:
Mobilization of the transcription factor NF-κB is an essential step for NK cell activation and proceeds its cytotoxicic activity and production of cytokines. To evaluate the impact of nicotine on NF-κB activity in NK cells, we sorted NK cells from the spleen of RAG2−/− mice, and cultured the isolated NK cells alone or with nicotine for 24 h. We performed a series of real-time PCR experiments looking at changes in transcript abundance, and saw that addition of nicotine suppressed gene transcription of NF-κB, and IKKα, an alternative regulator of NF-κB in NK cells (Figure 4). To determine if nAChR β2 is involved, we cross-bred RAG2−/− with nAChR β2−/− mice to generate double knockout mice. When NK cells derived from these mice were used, the effect of nicotine on NF-κB and IKKα transcription becomes minimum(Figure 4). Thus, nAChR β2 mediates the effects of nicotine on NK cell transcription genes that are critical for their functions.

pone-0057495-g004: Nicotine inhibits NF-κB activation in NK cells through nAChR β2.NK cells were sorted from splenocyte single cell suspensions of RAG2−/− and RAG2−/−β2−/− mice. NF-κB and IKKα mRNA of sorted NK cells in β2+/+ or β2−/− mice received nicotine (Nic) was measured by qRT-PCR. The data of one experiment out of two performed is shown, n = 3–4 mice/group. P values, Student’s t-test, *p<0.05.

Mentions:
Mobilization of the transcription factor NF-κB is an essential step for NK cell activation and proceeds its cytotoxicic activity and production of cytokines. To evaluate the impact of nicotine on NF-κB activity in NK cells, we sorted NK cells from the spleen of RAG2−/− mice, and cultured the isolated NK cells alone or with nicotine for 24 h. We performed a series of real-time PCR experiments looking at changes in transcript abundance, and saw that addition of nicotine suppressed gene transcription of NF-κB, and IKKα, an alternative regulator of NF-κB in NK cells (Figure 4). To determine if nAChR β2 is involved, we cross-bred RAG2−/− with nAChR β2−/− mice to generate double knockout mice. When NK cells derived from these mice were used, the effect of nicotine on NF-κB and IKKα transcription becomes minimum(Figure 4). Thus, nAChR β2 mediates the effects of nicotine on NK cell transcription genes that are critical for their functions.

Bottom Line:
Further, nicotinic suppression of NF-κB-induced transcriptional activity in NK cells is dependent on nAChR β2.This nAChR subtype also plays a large role in the NK cell-mediated control of melanoma lung metastasis, in a murine lung metastasis model exposed to nicotine.Our findings suggest nAChR β2 as a prominent pathway for nicotine induced impairment of NK cell functions which contributes to the occurrence of smoking-related pathologies.

ABSTRACTCigarette smoke exposure markedly compromises the ability of the immune system to protect against invading pathogens and tumorigenesis. Nicotine is a psychoactive component of tobacco products that acts as does the natural neurotransmitter, acetylcholine, on nicotinic receptors (nAChRs). Here we demonstrate that natural killer (NK) cells strongly express nAChR β2. Nicotine exposure impairs the ability of NK cells to kill target cells and release cytokines, a process that is largely abrogated by nAChR β2 deficiency. Further, nicotinic suppression of NF-κB-induced transcriptional activity in NK cells is dependent on nAChR β2. This nAChR subtype also plays a large role in the NK cell-mediated control of melanoma lung metastasis, in a murine lung metastasis model exposed to nicotine. Our findings suggest nAChR β2 as a prominent pathway for nicotine induced impairment of NK cell functions which contributes to the occurrence of smoking-related pathologies.